Michelle Obama’s roots have been traced back to a six-year-old slave girl who was bequeathed to her owner’s heirs along with his household possessions and cattle.

The child, described in the will of David Patterson simply as “the negro girl Melvinia”, was uprooted from her plantation home in South Carolina and shipped to the US state of Georgia in 1852.

There, while still a teenager, she gave birth to the son of a white man – a union of dubious status that would have been looked down upon at the time but one which produced the First Lady’s maternal great-great-grandfather.

The wife of President Barack Obama grew up with only a vague awareness of her ancestry, but a paternal great-great-grandfather, Jim Robinson, who was also a slave, was identified during the presidential election campaign.

The five-generation journey from a plantation to the White House, unveiled on Wednesday by Megan Smolenyak, a genealogist working with The New York Times, for the first time draws a direct line on the First Lady’s family tree to America’s history of slavery.

The First Lady is hailed by many as a symbol of the advancement of black Americans, and Mrs Obama’s genealogy is far more relevant to most African-Americans than that of her husband, the son of a white American mother and a black father from Kenya.